In-plane thermal conductivity measurement of microscale polymer films using a reusable micro-thermocouple

Polymers serve as encapsulating materials for electronic devices, making it crucial to investigate their thermophysical properties. In this work, a novel 2 omega method for assessing the in-plane thermal conductivity of polymer films is proposed. A reusable micro-thermocouple, serving as both a heating wire and a sensor, is used with silver paste as the interstitial material in contact with the test film. By comparing the 2 omega voltages under both contact and non-contact conditions, the thermal impedance is determined. The thermal conductivity is directly calculated by determining the slope of the real part of the thermal impedance against the logarithm of frequency. Theoretical analysis shows that the influences of contact thermal resistance and radiation heat loss are negligible. To validate the accuracy of the method, measurements were repeated on polyimide and polyester films under various contact conditions. The results demonstrate consistency and align with those obtained using the laser spot periodic heating technique.